1. Field of the Invention
This invention relates to a television system containing an apparatus for reproducing picture information recorded on a video compact disk (CD) and in particular to a television system containing a video CD reproducer adapted to reproduce picture information recorded on a video CD complying with more than one standard for displaying a picture.
2. Description of the Related Art
For example, the configuration shown in FIG. 11 is known as such a television system containing a video CD reproducer. FIG. 11 is a block diagram showing a conventional signal processing system from reproducing picture information recorded on a video CD to display a picture. In the figure, numeral 1 is a video CD, numeral 2 is a CD signal processor, numeral 3 is an MPEG (Moving Picture Experts Group) decoder, numeral 4 is a video encoder, numeral 5 is a synchronizing circuit, numeral 6 is a video signal processor, numeral 7 is a cathode-ray tube (CRT), and numeral 8 is a deflection circuit. In the figure, a video CD reproducer, which will be hereinafter referred to as a CD player, is shown to the left of the broken line and a television set is shown to the right of the broken line, wherein a picture reproduced from picture information on the video CD 1 is displayed on the television.
Only the necessary part of picture information reproduced from the video CD 1 is processed by the CD signal processor 2, and the result then is supplied to the MPEG decoder 3, which performs decoding processing such as data expansion based on a synchronizing signal from the synchronizing circuit 5 for providing a digital video signal. This digital video signal is supplied to the video encoder 4, which converts it into an analog signal and further adds a synchronizing signal from the synchronizing circuit 5 to the analog signal for converting the analog signal into a standard composite color video signal. Like a reception composite color video signal supplied from a reception system (not shown), the composite color video signal is processed by the video signal processor 6 and supplied to the CRT 7. The video signal processor 6 separates the synchronizing signal from the composite color video signal and the deflection circuit 8 (consisting of horizontal and vertical deflection channels) deflects the CRT 7 in synchronization with the synchronizing signal, whereby a picture reproduced from picture information on the video CD 1 is displayed on the screen of the CRT 7.
Picture information digitized and compressed complying with the MPEG standard is recorded on the video CD 1 played back by such a television system containing a video CD reproducer. CDs on which the picture information is recorded are roughly classified into those containing information recorded in the format compatible with the NTSC (National Television System Committee) system, which will be hereinafter referred to as NTSC system video CDs, and those containing information recorded in the format compatible with the PAL (Phase Alternation by Line) system, which will be hereinafter referred to as PAL system video CDs. On the NTSC system video CD, picture information is recorded in the data format of the number of frames per second 30, the number of horizontal scanning lines per frame 240, and the number of dots per line 352. On the PAL system video CD, picture information is recorded in the data format of the number of frames per second 25, the number of horizontal scanning lines per frame 288, and the number of dots per line 352.
The picture information is converted into a digital video signal by the MPEG decoder 3 so that a picture can be displayed on the television. The MPEG decoder 3 is adapted to convert the picture information to be reproduced into a video signal matching the television system for supply to the television regardless of whether the video CD is an NTSC or PAL video CD.
For example, to display picture information recorded on a PAL system video CD on an NTSC system television set, the MPEG decoder 3 converts the picture information on the PAL system video CD into digital video signal with the number of fields per second 60, the effective number of lines per frame 480, and the number of dots per line 704. Of course, for an NTSC system video CD, the MPEG decoder 3 provides such a digital video signal. To perform such conversion, the same picture information is read twice from a memory contained in the MPEG decoder 3 for substantially doubling the number of frames and the number of lines. However, to display picture information recorded on a PAL system video CD on an NTSC system television set, if the number of lines of the picture information recorded on the PAL system video CD is simply doubled (288.times.2=576), the result does not match the effective number of lines of the NTSC system television set (480). Then, for example, picture information of "576-480=96 lines" is deleted in the vertical direction from the original picture information for display on the television.
To display picture information recorded on an NTSC system video CD on a PAL system television set, the MPEG decoder 3 converts the picture information on the NTSC system video CD into digital video signal with the number of fields per second 50, the effective number of lines per frame 576, and the number of dots per line 704. Of course, for a PAL system video CD, the MPEG decoder 3 provides such a digital video signal. Also in this case, if the number of lines of the picture information recorded on the NTSC system video CD is simply doubled (240.times.2=480), the result does not match the effective number of lines of the PAL system television set (576). Then, for example, a signal of "576-480=96 lines" is added to the original picture information in the vertical direction for display on the television.
However, to play back video CDs of different types on which video signals are recorded in accordance with different television standards by a CD player contained in a television as described above, the following problems arise:
(1) If the picture information recording system on a video CD differs from the television system, the aspect ratio of a picture displayed on CRT differs from that of the CRT screen, thus the displayed picture is distorted and becomes difficult to see. Such distortion will be hereinafter referred to as aspect distortion and is discussed below: PA1 (2) To display a picture on an NTSC system television set using picture information reproduced from a PAL system video CD, 96-line picture information is lost, as described above. Also, to display a picture on a PA1 (3) Normally, additional information such as information on a moving picture such as the title, creator name, and preceding and following chapters of the moving picture and time-of-day information is recorded on a video CD in addition to picture information of the moving picture. The additional information can be read and displayed on a screen as required. However, to display such additional information on the screen, hitherto, a PinP (picture in picture) system has been adopted for displaying an image of the additional information in a part of the moving picture display area. However, in the PinP system, a part of the moving picture display area is lost and the PinP area becomes a visually offensive feature.
To display picture information recorded on a PAL system video CD on an NTSC system television set, a picture from which 96-line picture information is deleted in the vertical direction is displayed on the television, as described above. Thus, the actual picture displayed on the television is extended to 576/480 times as large as the original picture in the vertical direction, for example, as shown in FIG. 12 (a). Therefore, aspect distortion occurs as a phenomenon such that a round picture is displayed as a lengthwise extended picture. PA2 To display picture information recorded on an NTSC system video CD on a PAL system television set, a picture to which 96-line picture information is added in the vertical direction is displayed on the television, as described above. Thus, the actual picture displayed on the television is shrunk to 480/576 times as large as the original picture in the vertical direction, for example, as shown in FIG. 12 (b). Therefore, aspect distortion occurs as a phenomenon such that a round picture is displayed as a widthwise extended picture.
system television set using picture information reproduced from an NTSC system video CD, screen flicker is prominent, because human eyes are sensitive to flicker on a picture having a field frequency of 50 Hz.